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Pre-proposal to the United States Environmental Protection Agency

Innovations Grant Program
August 19, 2002

Submitted by
Connecticut Department of Environmental Protection
Bureau of Water Management
79 Elm Street
Hartford, CT 06106-5127

Monitoring of Municipal Sewage Treatment Plants For Pollutant Credit Exchange and Compliance

The Connecticut Department of Environmental Protection (DEP) is implementing legislation authorizing the issuance of a watershed general permit to regulate the discharge of nitrogen from municipal point sources and the institution of a nitrogen credit-trading program pursuant to the approved Total Maximum Daily Load (TMDL) for Long Island Sound. The General Permit (GP) issued by DEP regulates 79 publicly-owned wastewater treatment works (POTW) located throughout the state of Connecticut and establishes the most expansive program of water pollutant trading in the U.S. This program is projected to save the state $200 million in capital construction costs and will accelerate the schedule for meeting the TMDL wasteload allocation (WLA) for point sources by providing economic incentives for those POTWs that move quickly to remove nitrogen and comply with the limits in the GP. There is potential to expand this approach within Connecticut to other sources, including nonpoint sources. It can also serve as a model for other states that are facing similar TMDL implementation challenges not only as a cost-effective approach to reducing a pollutant from numerous sources, but also as an innovative approach to integrating the allocation of State Revolving Fund funding with permitting and enforcement programs.

Despite the anticipated value and cost savings from implementing the Nitrogen Credit Exchange (NCE) in Connecticut, there are concerns over the reliability and accuracy of standard monitoring protocols. The GP sets monitoring frequency based on plant size. Facilities with design flows greater than or equal to 10 MGD are required to monitor the final effluent at a minimum frequency of twice per week while smaller plants are required to monitor at a minimum of once per week. Each sample must be a 24-h composite sample and be analyzed according to methods approved by EPA. While it is believed that this frequency will be adequate to characterize an individual plant's nitrogen load and that analytical protocols are proven suitable for wastewater analysis, local plant variability and weather effects may produce enough statistical error to require additional analyses. There have been no detailed studies of effluent nitrogen variability on daily to weekly time scales at Connecticut facilities. Given the economic impact of the nitrogen trading program at municipal and state levels, DEP needs to provide assurance that monitoring to generate credits is reasonably accurate and conducted at the most cost-effective frequency possible. Further, this evaluation will assist scheduling of compliance checks and reduce the possibility that nitrogen loads to Long Island Sound are erroneously under reported.

Over the past decade, DEP has worked with the EPA Long Island Sound Study (LISS) and the Water Environment Research Foundation (WERF) to develop a framework for a Nitrogen Credit Trading Program. Connecticut and New York jointly drafted the TMDL to address seasonal low oxygen problems in Long Island Sound and with its approval in early 2001, Connecticut is faced with reducing nitrogen loads from 79 POTWs scattered throughout the state. Nitrogen is the primary pollutant linked to an extensive low-oxygen (hypoxia) problem that affects up to half of Long Island Sound's 1300 square miles of bottom during periods of summer stratification when bottom waters are prevented from mixing with surface waters. The nitrogen fuels the growth of algae, which eventually decays after it settles to the bottom of the Sound. The Sound is so heavily enriched that the microbial decay drives oxygen to levels low enough to create unhealthy or even lethal conditions for aquatic life.

The TMDL1 to correct this problem, which was approved by the EPA in April 2001, requires a 58.5% reduction in baseline anthropogenic nitrogen loads from sources in Connecticut and New York by the year 2014. Using the trading framework developed by the LISS and WERF2 as a starting point, DEP proposed legislation3 to establish a nitrogen general permit and a nitrogen credit-trading program for municipal point sources throughout Connecticut. Public Act 01-180 was passed in June 2001 and established a Nitrogen Credit Exchange (NCE) to be guided by a Nitrogen Credit Advisory Board (NCAB) under the authority of the Commissioner of the DEP.

The Nitrogen General Permit is key to the success of Connecticut's trading program. It collectively regulates 79 POTWs located throughout the state and establishes the basis for the most expansive program of water pollutant trading in the U.S. The GP sets annual nitrogen limits for each POTW that are increasingly stringent until the final WLA is attained in 2014. POTWs can comply by either treating or by purchasing credits from the Nitrogen Credit Exchange annually. The nitrogen credit-trading program is both innovative and essential to resolve the complex water quality problems in Long Island Sound in a cost-effective manner. The proposed program links together Connecticut's existing general permitting authorities, the State Revolving Loan Program (SRF) and other salient features of state and federal laws to form a comprehensive regulatory program to assure compliance with Connecticut's nitrogen reduction requirements under the TMDL. However, the success or failure of this program, and the improvement to the health of LIS, rely heavily on our ability to accurately monitor nitrogen loads from the 79 facilities incorporated in the GP.

The first task under this proposal would be to conduct high-intensity monitoring at four to six municipal POTWs representing a range of sizes, nitrogen removal capability, and susceptibility to weather changes (e.g., infiltration from wet conditions). Samples would be collected at the facilities by automatic sampler for later analysis. One larger facility would be selected to utilize online real-time nitrogen analysis systems. The real-time analysis system will be installed and operated for a period of one year. The facility utilizing the online real real-time system would also conduct the same high-intensity monitoring. Laboratory analyses would be conducted using EPA standard protocols under an approved EPA Quality Assurance Project Plan (QAPP). Frequency would be at least four times per day over a two-week period once during each of four seasons. This sampling strategy would experience a full range of wet/dry and warm/cool conditions that might affect nitrogen removal capability, and would also fully examine day to day fluctuations in effluent nitrogen strength.

Data would be analyzed statistically to identify and develop a sampling scheme that would maximize precision in monthly nitrogen load calculations. It is possible that certain conditions might need to be targeted for more frequent sampling, such as higher spring flows that might vary with rainfall, or certain days of the week that might reflect maximum or minimum concentrations related to business days vs. weekend conditions. The data could also help guide compliance monitoring programs to ensure reliable, yet cost-effective checks on self-monitoring programs. In both cases, it is the desire of DEP to gain the most reliable nitrogen load estimations with the minimum resources, saving money for the municipalities and DEP while not compromising the credibility of the NCE.

In addition to the first year's assessment of monitoring, DEP proposes to evaluate the program's effectiveness in regulating point source discharges as related to the accuracy of nitrogen load estimates. Because the first year of operation of the NCE (2002) will be based on the requirements of the GP noted above, this monitoring study will allow estimates of error under GP protocols compared to proposed revisions in the monitoring program that the study might support. Since one possibility is that the GP monitoring requirements are excessive, it will also be possible to demonstrate what significance there might be to an increase in sampling error under a reduced sampling schedule. Any number of "what if" scenarios can be constructed using the database generated in this study, allowing an optimal monitoring program to be selected from a range of potential error conditions.

The third task would seek to maximize efficiency of quality assurance for individual facility monitoring programs (e.g., duplicates, blanks) and frequency of independent (e.g., DEP) split sampling or compliance sampling. This analysis of the data would focus on error in split and duplicate samples, perhaps using two labs for some of the analyses, to ascertain level of reliability at the facility level and increase value of compliance sampling at the state level. An attempt will also be made to identify attributes associated with unreliable data or operational problems leading to development of a "risk-based" compliance/technical assistance program.

Broader Application
Connecticut has embarked on a complex, but highly innovative, general permitting and trading program that has not been implemented to this degree anywhere else in the U.S. Of prime consideration in evaluating the success of the point source program being implemented in 2002 and the potential for change in sampling frequency and timing, including compliance sampling without compromising nitrogen load estimation accuracy. In addition is the learning value it may hold for other states implementing complex TMDLs that require accurate reporting of pollutant loads. Estuaries like the Chesapeake Bay and Gulf of Mexico are addressing hypoxia problems similar to those observed in Long Island Sound and are planning and implementing nutrient control programs in multi-state areas. The successes and failures of Connecticut's program will yield valuable lessons for these and other areas where closed system trading under a general permit makes economic and environmental sense and the credibility of the program relies on accurate monitoring of effluent parameters.

Final products of this project will include:

  1. A technical assessment of the intensive monitoring effort along with a comparative analysis of utilization of online real-time nitrogen analysis. (Task 1)
  2. An evaluation of the change in error related to a range of monitoring schedules (Task 2)
  3. An evaluation of quality assurance sampling and compliance sampling (Task 3)

Budget (estimated for a two-year study effort) [REDACTED BY US EPA]


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